eWan supports QR code. If you are creating an event you can print the QR code to the poster and users can simple scan it to chat about your event.
To log in you only need to use a facebook account, however chatting is anonymous and you can choose any proper user name.
Groups can either be public and visible for anyone, ranked by distant to where it was created, or it can be private and only accessible through invite.
eWan icon is made by [email protected].